Electromagnetic waves have been used in various applications to supply energy to objects. Radio frequency (RF) electromagnetic energy, for example, may be supplied using a magnetron, which is typically tuned to a single frequency for supplying electromagnetic energy only at that frequency. One example of a commonly used device employing electromagnetic energy is a microwave oven. Typical microwave ovens supply electromagnetic energy at the single frequency of 2.45 GHz. To increase the distribution of electromagnetic waves, the typical microwave oven includes a metallic fan, often placed behind a grill in the oven, to disturb standing wave patterns in the electromagnetic radiation and achieve more uniform energy distribution in the oven's cavity. Objects in containers (e.g., liquids, etc.) may also be heated by transferring electromagnetic energy to elements located on the container walls, thereby heating the walls and the contents of the container.